This is a multicenter randomized double-blind placebo controlled parallel group study evaluating the efficacy and safety of GC150526 or placebo in patients with a clinical diagnosis of acute stroke. This drug is a potent glycine antagonist. Glycine is a co-agonist of the NMDA receptor for glutamine-induced and neuroexcitation. Since this NMDA receptor by stimulation of this NMDA receptor by glutamate may be cytotoxic during cerebral ischemia, antagonism of this receptor may be beneficial.